Lecture 2 Flashcards
How many neurons in the CNS?
100 billion
What are the 4 key components of typical neurons?
- Soma (cell body)
- Dendrites
- Axon
- Nucleus
How many types of neurons are there? why?
many
because they are specialized for the type of information they’re processing
different types found in different areas
how does info flow through a neuron?
comes in through the dendrites, integrated in the soma, then a decision is made about whether to fire an action potential through the axon
Can changes to the nucleus be short term or long term?
short (electrical )and long term (genetic expression)
What can input from dendrites to the nuclear result in?
either an electrical signal, or changes in gene expression
What can input from dendrites to the nuclear result in?
either an electrical signal, or changes in gene expression
Which pat of the neuron has the genetic material?
nucleus
What are the main functions of glial cells?
- maintain ionic composition of neurons
- modulate the rate of nerve cell propogation (make speed of transmission down an axon e.g. meylein)
- modulate synaptic function through uptake and metabolism of neurotransmitters
- act as scaffolding for neurons during development (make sure neurons are where they are supposed to be and don’t move around)
- repair neural injury + fighting off infections
3 types of Glial cells
- Astrocytes
- Oligodendrocytes
- Mictroglia
Oligodendrocytes are responsible for
myelin sheath
Glial cells are NOT involved in?
electrical signalling
Why is it that neurons are able to communicate electrical signals?
the separation of positively and negatively charged isons across the semi permeable membrane of the neuron
- this results in a potential difference in charge (voltage) across the membrane, which is know as the resting membrane potential
What is the typical resting membrane potential?
-40 to -90 mV
Describe the structure of a membrane?
A lipid bilayer of cells that is hydrophobic (repels water)
- this layer repels
Has membrane spanning protein channels for specific ions
why are the heads of the channels sticking out? (lipid bilayer)
describe the water versus lipid separation and how it makes the membrane semi permeable
*** this is referring to hydrophobic layer and hydrophilic layer + specialize protein channels
they are composed of different things at different sides
the heads of the layer are going to point towards the water end and awar from the fat ends versus the heads like like water point
what are the different changes to voltage that occur
- Hyperpolarization
- Depolarization
- Threshold potential
what is threshold potential?
point at which the neuron becomes sufficiently depolarized to result in an action potential
When do neurons fire/why
other neurons are having a hyperolarizing or depolarizing effect on the neuron, if the cumulative effects of this cause it to reach the threshold potential then the neuron ‘fires’
When do neurons fire/why
other neurons are having a hyperolarizing or depolarizing effect on the neuron, if the cumulative effects of this cause it to reach the threshold potential then the neuron ‘fires’
which type of charge can result in depolarization?
positive charge
which type of charge can result in depolarization?
positive charge (idk if this is true because the inside of the cell is negative and then does depolarization make it more negative or positive? check in textbook)
What happens when depolarization reaches the threshold?
what is this called?
surge of positive charge in the neuron
called an action potential
what determines how strong a signal is?
the mount of action potentials within a certain amount of time (the rate at which the action potentials occur)
What allows the action potential to occur?
the channels in the membrane are sensitive to changes in voltage, so when the depolarization threshold is met they can sense it and then change -> so the channel that allows sodium to enter the cell open up, and this is what causes the depolarization spike in the neuron
What happens after the action potential?
the membrane has active transporters that function as ‘pumps’ that remove the positive charge from the neuron
this overshoots the resting potential and then returns to resting
Why is it important to understand action potentials?
because some of the channels involved in the process are affected by certain drugs
What is the sodium potassium pump? why does it exist?
the membrane is still somewhat permeable and sodium slowly leaks into the cell making it more positive, so the sodium potassium pump maintains/restores the membrane potentianl
he calls it the ATPase pump (not sure if its the same??)
kicks out 3 sodium ions for each 2 potasssium ions that are brought in -> so the net charge becomes more negative.
What is the refractory period and why does it occur?
ww
What are the nodes of ranvier
small opening of the meylin sheath where you have a setup of negative/positive charge -> action potential is able to jump
what is altatory conduction?
hh
What happens when an action potential reaches the end of the axon?
electrical signal is converted to chemical ->
action potential enters the terminal of the presynaptic neuron, change in membrane potential leads to opening of calcium channels, calcium enters the neuron and causes the neurotrasmitter filled vesicles to fuse with the plasma membrane, neurotransmitter is released into the synapse
how do action potentials travel?
so when they travel it’s actually through localized effect on the cell, so if its going down the axon it’s just the area near where the action potential is occuring that has the positive charge inside and negative outside, the rest of the cell is what it would be at resting -> see lecture and maybe look up in textbook for clarification
which direction is information transfered in the synapse?
usually one way but can be retrograde
which direction is information transfered in the synapse?
usually one way (from pre synaptic to post synaptic neuron) but can be retrograde and affect the pre synaptic neuron too
what is the difference between synaptic communication and endocrine system
endocrine system going through the whole circulatory system -> versus synapse is very precise and localized
how are neurotransmitters synthesized?
ss
note that the synthesis of neurotransmitters are unique for each so make sure to look at this
*note for me
NOTE he said synaptic structures are important to know
pre synaptic:
- synaptice bouton
- synaptic vesicles
- secretory vesicles
- docking complex
post synamptic
- synaptic cleft
- post synaptic density
what are the vesicles formed from?
endocytotic folds of the presynaptic membrane
secretory vesicles are
- fewer than synaptic vesicles
- larger than (avobe)
- contain neuropeptides
- neuropeptides are…..
***note he said to know that neuropeptides exist and are important but i don’t think we need to know in a ton of detail
Describe the docking complex
s
Describe the synaptic cleft
w
see overview of chemical transmission
d
what are the 2 types of neurotransmitter (NT) receptors?
- > NT fits like a key in a lock in the receptor
1. ionotropic receptors (or ligand-gated) -> can think about these as fast/immediate receptors related to changes in the electrical signal , quick acting
2. meabotropic receptors -> lead to metabolic changes, more long term genomic changes in the post synaptic neuron and these will ultimate change the way the neuron behaves but it’s more long term
talked about agonist and antagonist pharmacological actions that act of the ligand receptor
r
Describe ligand-gated ion receptors
d
Describe metabotropic receptors
he said we don’t need to memorize this just need to understand that these exist and are different from ligand gated ionitropic recepctors/
more generall see slide
don’t need to memorize or know the different pathways for the types of these receptors
how many types of neurotransmitters are there?
what are the 2 broad categories of them?
more than 100
small molecule (includes biogenic amines)
neuropeptides (3 amine acids)
What is a neurotransmitter
d
What are the necessary characteristics of a neurotransmitter?
e
what are the small molecule neurotransmitters?
list
note not gonna talk much about aspartate**
note
what are all the possible sites of drug action
note huge list see slide, figure out a strategy to group and memorize
what are the 2 important subtypes of acetlycholine receptors
nicotinic (ligand ion channel)
muscarinic (matabotropic)
note that acetlycholine doesn’t differentiate and attaches to both, but there are some substances that bind to one or the other
What does “maintain ionic composition of neurons” mean? what does this?
Help to maintain the difference in charge between the inside and ouside of a neuron
Glial cells support this process
What is the voltage accross the membrane?
voltage is the potential difference in charge across the membrane and is called the resting membrane potential
What is an ion?
an element/chemical (e.g. sodium) that has a certain charge when disolved in solution
the different chemicals can carry different charges
What is voltage dependent permeability?
The ermeability of Na+ and K+ channels depends on trans-membrane potential
Depolarization leads to increase in conductance of Na+ and K+ channels
That is, ionic permeability is voltage-sensitive
Na+ conductance change is faster (earlier) than K+ conductance change (later)
